The present invention relates to a printed circuit board adapter, supplying apparatus and method for use in a printed circuit board drilling machine. More particularly, the invention is concerned with a printed circuit board supplying apparatus and method capable of storing and conveying printed circuit boards in an oblique position and also an adapter or base plate for mounting a circuit board thereon so that printed circuit boards can be supplied to the drilling machine under standard conditions regardless of the number and location of fixing pins.
In general, a printed circuit board to be fed to a printed circuit board drilling machine has a laminated structure composed of an upper plate, a printed circuit board and a lower plate which are stacked in layers. These layers are integrally fixed to each other usually by means of two to four reference pins which are pressed into the laminated structure. These reference pins are fixed or clamped by suitable fixing structure disposed on a drilling machine table. Therefore, it is necessary to locate the reference pins in conveying the printed circuit boards.
A known printed circuit board supplying apparatus and method for supplying printed circuit boards to a drilling machine conveys the printed circuit boards in an oblique posture. Such a printed circuit board supplying apparatus is disclosed, for example, in Japanese Patent Unexamined Publication Nos. 60-262720, 60-263639, 62-259741, 62-259742, and 62-297042, and Japanese Utility Model Unexamined Publication Nos. 61-137446 and 61-201748. This type of printed circuit board supplying apparatus generally has power driven rollers for conveying the printed circuit boards, so that the supplying apparatus has a compact and simple construction. In addition, this type of apparatus advantageously enables easy replacement of the printed circuit boards in a stocker during the drilling operation.
In the foregoing known printed circuit board supplying apparatus in which the printed circuit boards simply rest on power-driven rollers, stoppers are disposed along the conveying path of the printed circuit board in order to locate the printed circuit boards such that the reference pins on the printed circuit boards being conveyed contact with and are stopped by the stoppers.
This arrangement does cause the printed circuit board to be undesirably tilted due to inertia of the upper portion of the printed circuit board when the reference pins are stopped by the stoppers, particulary when the conveying speed is high. In such a case, the reference pins of a tilted circuit board may not be aligned with the fixing or clamping device provided on the drilling table, with the result that the printed circuit board is not properly supplied to the table for a drilling operation. To avoid this problem, it has been found necessary using known procedures to slow the conveying speed considerably to avoid the inertia and tilting problems, e.g. 13 to 15 meters per minute.